Hydraulic pressure generating device

ABSTRACT

A hydraulic pressure generating device having a housing with air holes formed at least in its upper and lower walls, a partition wall with air holes to divide the housing into upper and lower rooms, a fan located in the upper room of the housing, a pressure compensation variable discharge type pump, a motor mounted in the lower room for driving the pump, and an oil tank disposed in the lower room and having soaked therein the pump. In this case, when the fan is operated, air is sucked into the housing from the air holes bored in the lower wall of the housing and is discharged out of the housing through the air holes bored in the upper wall of the housing to thereby cool the pump and the motor effectively.

United States Patent [191 Kikutsugi et al.

[ 1 Feb. 12, 1974 1 HYDRAULIC PRESSURE GENERATING DEVICE [75] Inventors:Aisaku Kikutsugi, Kawasaki;

Yoshihisa Shimoyama, Tokyo, both of Japan [73] Assignee: KabushikikaishaTokyo Keiki (Tokyo Keiki Co., Ltd.), Tokyo, Japan 22 Filed: Feb. 2, 197221 Appl. No.: 222,848

[58] Field of Search... 417/367, 368, 222, 271, 313, 417/363, 366, 372,435; 165/47; 184/104 3,080,495 Sudmeier 417/415 2,136,098 11/1938Browne.... 417/363 X 1,953,473 4/1934 Fedders 417/363 X 2,297,220 9/1942Hintze 417/372 1 3,369,736 2/1968 C0leman.. 417/372 3,372,863 3/1968Bloom i 417/372 3,156,409 11/1964 Paugh 417/372 3,478,958 11/1969l-linck 417/312 X Primary ExaminerWilliam L. Freeh AssistantE.mminerRichard Sher Attorney, Agent, or FirmGeorge B. Oujevolk [5 7ABSTRACT A hydraulic pressure generating device having a housing withair holes formed at least in its upper and lower walls, a partition wallwith air holes to divide the housing into upper and lower rooms, a fanlocated in the upper room of the housing, a pressure compensationvariable discharge type pump, a motor mounted in the lower room fordriving the pump, and an oil [56] References Cited tank disposed in thelower room and having soaked UNnED STATES PATENTS therein the pump. Inthis case, when the fan is oper- 2550 754 5,195] Baker [65/47 ated, airis sucked into the housing from the air holes 2347:9412 8/1953 Shaw v47/435 bored in the lower wall of the housing and is dis- 334360910/|967 Dubin [65/47 charged out of the housing through the air holesbored 3,694,108 9/1972 Pensa 417/222 in the upper wall of the housing tothereby cool the 3,487,431 12/1969 Forkner. 417/372 X pump and the motoreffectively. 2,299,233 10/1942 Hoffer 417/222 1 2,510,632 6/1950Hemphill 417/366 9 Claims, 5 Drawing Figures 1 HYDRAULIC PRESSUREGENERATING DEVICE BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates to a hydraulic pressure generating device.

2. Description of the Prior Art An ordinary hydraulic pressuregenerating device such as shown in FIG. 1 which is commonly referred toas a power unit for a numerically-controlled machine tool comprises aconstant discharge type pump 1, a motor 2 for driving it, and an oiltank 3 containing an actuating oil 4 (hereinafter referred to as anoil). In this device, when the motor 2 rotates, the oil 4 is introducedthrough a filter 5 and a hose 6 into the pump 1, from which a constantamount of oil per unit time is continuously discharged. One part of thedischarged oil is returned to the oil tank 3 through a line filter 7, aload 8 and a cooler 9. While, the oil discharged from the constantdischarge type pump 1 is mostly fed through a relief valve 10 to theinput side of the cooler 9 and is thereby cooled together with the oilapplied thereto through the load 8 and then returned to the oil tank 3.Reference numeral 11 indicates a pilot line of the relief valve 10, 12 adrain pipe of the pump 1 and 13 a safety valve of the cooler 9.

With such a conventional device, a substantially constant amount of oilis always discharged from the pump 1 irrespective of a variation in theload 8 and the discharged oil is mostly returned to the oil tank 3through the relief valve 10. Therefore, the utilization efficient factorof the oil is poor and a loss, viewed from the overall structure of thedevice, is great and, in addition, the temperature of the oil rises whenit passes through the relief valve 10, which causes large vibration ofthe overall device. Further, since the oil is compressed by the reliefvalve 10, it rapidly deteriorates, which results in various badinfluences such as generation of wear, damage and vibration of theinstruments using the oil and so on.

SUMMARY OF THE INVENTION The present invention is to provide a hydraulicpressure generating device which is free from the aforementioned defectsexperienced in the prior art, and hence is highly efficient, capable ofsuppressing heat generation of the oil used, extending the lifetime ofthe instruments and oil and preventing deterioration of the oil and isinexpensive and good in appearance.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram showing aconventional type of hydraulic pressure generating device;

FIG. 2 is a schamatic diagram illustrating a hydraulic pressuregenerating device of the present invention;

FIG. 3 is a perspective view of the device of this invention;

FIG. 4 is a fragmentary cross-sectional view of the device of FIG. 3;and

FIG. 5 is a cross-sectional view showing one example of a pump for usein this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIGS. 2 to 5,one example of the hydraulic pressure generating device of thisinvention will hereinafter be described. In FIG. 2 reference numeral 21designates a pressure compensating variable discharge type pump, whichis driven a motor 22. Reference numeral 23 indicates an oil tank and 24an oil contained therein. Reference numeral 18 identifies a load drivenby the pump 21.

As shown in FIG. 3, a housing 25 as of iron or like material isprovided, which is divided by a partition wall 26 into upper and lowerrooms 27 and 28 and a plurality of air holes 29 are formed in thepartition wall 26. In the upper room 27 an exhaust fan 30 is disposed,which is driven by a motor, though not shown. In the lower room 28 thepump 21, the motor 22 and the oil tank 23 are housed. In this case, thepump 21 is disposed below the oil level 24a in the oil tank 23. In theillustrated example the motor 22 is attached to an upper wall 23a of theoil tank 23 with its rotary shaft 22a being held vertically and the pump21 is disposed in the oil 24 and a rotary shaft 21a of the pump 21 iscoupled by a coupling 31 with that 22a of the motor 22. Referencenumeral 32 designates a fixture of the motor 22, 33 a fixture of thepump 21, 34 an air escape bored in a case 21b of the pump 21 near theend of the shaft 210 at such a position as not to affect the bearingsupport, 340 an ordinary drain port and 35 a hose for supplying the oildischarged from the pump 21 to the outside, which hose is preferred tobe formed of rubber or like elastic material.

The horizontal area of the oil tank 23 is selected to be relativelysmaller than that of the lower room 28 of the housing 25, many radiationfins 36 are mounted on the outside of the oil tank 23 and slit-like airholes 37a and 37b are formed in the upper and lower walls 25a and 25b ofthe housing 25. Reference numeral 38 indicates support legs forsupporting the oil tank 23. Between the legs 38 and the oil tank 23 thelegs legs 38 and the lower wall 25b of the housing 25 are interposedvibration-proof members 39 as of rubber to prevent transmission of thevibration of the motor 22 and the pump 21 to the housing 25 and,further, vibrationproof rubber members 41 may be interposed between thehousing 25 and its legs 40. In FIG. 4 reference numerals 42 and 43designate adjusting levers respectively one ends of which project fromthe upper wall 23a of the oil tank 23,the former being used foradjustment of a pressure compensator and the latter for adjustment ofthe amount of the oil discharged by adjusting the inclination of aninclined plate of the pump 21.

FIG. 5 illustrates one example of the discharge type pump 21, in whichreference numeral 44 indicates its drive shaft, 45 a swash-plate(inclined plate), 46 a piston, 47 a cylinder block, 48 a valve plate and49 a pressure compensator. If necessary, filters may be provided beforeand after the pump 21.

With the present device described above, the hydraulic pressure of theoil discharged from the pump 21 and the amount of the oil dischargedtherefrom per unit time can be independently adjusted by manualoperation of the adjusting levers 42 and 43 and even when the pump 21 issoaked in the oil and, further, these values can be set at minimumvalues corresponding to the load, so that ineffective power can betheoretically minimized and the required capacity of the motor 22 can bedecreased. Further, although this device is applied to many kinds ofapparatus, the number of the kinds thereof in view of the capacity ofthe pump 21 can be decreased and the hydraulic pressure generatingdevice can be standardized and mass produced.

As will be apparent from FIG. 3, by the rotation of the fan 30, airenters the housing 25 from the air holes or slits 37b bored in the lowerwall 25b to cool the oil tank 23, the pump 21 and the motor 22 and flowsinto the upper room 27 from the air holes 29 of the partition wall 26and is then discharged from the housing 25 to the outside thereofthrough the air holes or slits 37a of the upper wall 25a. Accordingly,the oil tank 23, that is, the oil 24 is forcibly cooled, in which casethe fins 36 formed on the outside of the oil tank 23 enhances thecooling effect. In accordance with the present device the pump 21, themotor 22, the oil tank 23 and so on are covered with the housing 25, sothat the fins 36 on the oil tank 23 cannot be seen from the outside anddo not defile the appearance of the device. Further, the shapes of theair holes 29 and slits 37b are selected and a pressure-reduced air layeris produced by the operation of the exhaust fan 30 in the housing 25.The air layer and the housing 25 effectively suppress propagation ofmechanical vibration. In addition, the fins 36 serve to reinforce theoil tank 23.

By positioning the pump 21 below the oil level 24a of the oil 24, thesuction resistance of the pump 21 is decreased to improve conditions forthe generation of cavitation, which results in an increase in theefficiency of the pump 21 to alleviate the generation of vibration. Whenthe pump 21 is soaked in the oil 24 as in the illustrated example, thedrain pipe 12 depicted in FIG. 1 is unnecessary and accordingly themanufacturing cost can be curtailed and, at the same time, vibration ofthe pump 21 and propagation of its echo can be suppressed because thepump 21 is entirely enveloped in the oil. Further, the air escape 34formed in the pump 21 facilitates deflation of the pump 21, whichenables a supply of oil to internal lubricating units such as bearingsof the pump 21 and so on to provide for prolonged lifetime thereof.

The hose 35 directly connected to the discharge port of the pump 21 isformed of an elastic or flexible material such as rubber anddisconnected from the hose used on the side of the load. This allowsease in the fabrication of this device, enables prevention of mixing ofa foreign substance into the oil and effectively absorbs pulsation ofthe discharged oil.

With the present invention, a minimum amount of oil can be circulatedonly to the load and since no relief valve is required, heat generationdoes not occur. Further, the oil is not sheared by the relief valve, sothat deterioration of the oil is suppressed and heat generation is lowto provide for enhanced efficiency of the cooling achieved whennecessary and facilitate control of the oil temperature. Namely, thisinvention is capable of controlling the temperature and viscosity of theoil and maintenance of its quality which are important for lubricationof this kind of apparatus. Further, when employed in the hydraulicpressure system, wear of the pump shown in FIG. 5 is further reduced.The present invention dispenses with the line filter disposedunderstream of the pump which causes wear of the pump, permittingsimplification of the construction of the device, coupled with thenonuse of the relief valve.

It will be apparent that many modifications and variations may beeffected without departing from the scope of the novel concepts of thisinvention.

We claim as our invention:

1. In a hydraulic pressure generating device including a housing havingair holes formed at least in upper and lower walls thereof, a partitionwall dividing the housing into upper and lower rooms and having airholes, a fan disposed in the upper room of the housing, a pressurecompensation variable discharge type pump, a motor disposed in the lowerroom of the housing for driving the pump, and an oil tank disposed inthe lower room of the housing and having the pump immersed therein, theimprovement therein, wherein the shapes of the air holes formed in thepartition wall and in the lower wall of the housing are selected toprovide a pressure-reduced room in the housing, so that when the fan isoperated, air is sucked into the housing from the air holes formed inits lower wall and is discharged out of the housing from the air holesformed in its upper wall, so as to cool the pump and the motor.

2. A hydraulic pressure generating device as claimed in claim 1, whereinradiation fins are provided on the oil tank.

3. A hydraulic pressure generating device as claimed in claim 1, whereinan air escape is formed in the case of the pump.

4. A hydraulic pressure generating device as claimed in claim 1, whereina vibration-proof member is interposed between the oil tank and thehousing.

5. A hydraulic pressure generating device as claimed in claim 1, whereinthe housing is supported with a vibration-proof member.

6. A hydraulic pressure generating device comprismg:

a. a housing having air holes at least in upper and lower walls thereof;

b. a partition wall dividing the housing into upper and lower rooms andhaving air holes;

0. an exhaust fan disposed in the upper room of the housing;

d. a first motor disposed in the upper room for driving the fan;

e. a pressure compensation variable discharge type pump disposed in thelower room of the housing;

f. a second motor disposed in the lower room of the housing for drivingthe pump; and,

g. an oil tank disposed in the housing and having the pump immersedtherein, whereby when the fan is operated, air is sucked into thehousing from the air holes formed in the lower wall and then isexhausted out of the housing from the air holes formed in the upperwall.

7. A hydraulic pressure generating device comprising:

a. a housing having air holes at least in upper and lower walls thereof;

b. a partition wall dividing the housing into upper and lower rooms andhaving air holes;

c. an exhaust fan disposed in the upper room of the housing;

(1. a first motor disposed in the upper room for driving the fan;

e. a pressure compensation variable discharge type pump disposed in thelower room of the housing;

f. a second motor disposed in the lower room of the housing for drivingthe pump; and,

g. an oil tank disposed in the housing and having the pump immersedtherein, wherein the shapes of the air holes formed in the partitionwall and in the lower wall of the housing are so selected as to providea pressure-reduced room in the housing.

in claim 7 in which an adjusting means is provided for adjusting asetting pressure of the pump from the outside of the tank.

1. In a hydraulic pressure generating device including a housing having air holes formed at least in upper And lower walls thereof, a partition wall dividing the housing into upper and lower rooms and having air holes, a fan disposed in the upper room of the housing, a pressure compensation variable discharge type pump, a motor disposed in the lower room of the housing for driving the pump, and an oil tank disposed in the lower room of the housing and having the pump immersed therein, the improvement therein, wherein the shapes of the air holes formed in the partition wall and in the lower wall of the housing are selected to provide a pressure-reduced room in the housing, so that when the fan is operated, air is sucked into the housing from the air holes formed in its lower wall and is discharged out of the housing from the air holes formed in its upper wall, so as to cool the pump and the motor.
 2. A hydraulic pressure generating device as claimed in claim 1, wherein radiation fins are provided on the oil tank.
 3. A hydraulic pressure generating device as claimed in claim 1, wherein an air escape is formed in the case of the pump.
 4. A hydraulic pressure generating device as claimed in claim 1, wherein a vibration-proof member is interposed between the oil tank and the housing.
 5. A hydraulic pressure generating device as claimed in claim 1, wherein the housing is supported with a vibration-proof member.
 6. A hydraulic pressure generating device comprising: a. a housing having air holes at least in upper and lower walls thereof; b. a partition wall dividing the housing into upper and lower rooms and having air holes; c. an exhaust fan disposed in the upper room of the housing; d. a first motor disposed in the upper room for driving the fan; e. a pressure compensation variable discharge type pump disposed in the lower room of the housing; f. a second motor disposed in the lower room of the housing for driving the pump; and, g. an oil tank disposed in the housing and having the pump immersed therein, whereby when the fan is operated, air is sucked into the housing from the air holes formed in the lower wall and then is exhausted out of the housing from the air holes formed in the upper wall.
 7. A hydraulic pressure generating device comprising: a. a housing having air holes at least in upper and lower walls thereof; b. a partition wall dividing the housing into upper and lower rooms and having air holes; c. an exhaust fan disposed in the upper room of the housing; d. a first motor disposed in the upper room for driving the fan; e. a pressure compensation variable discharge type pump disposed in the lower room of the housing; f. a second motor disposed in the lower room of the housing for driving the pump; and, g. an oil tank disposed in the housing and having the pump immersed therein, wherein the shapes of the air holes formed in the partition wall and in the lower wall of the housing are so selected as to provide a pressure-reduced room in the housing.
 8. A hydraulic pressure generating device as claimed in claim 7, wherein said pump includes a casing in which an air escape is formed in the casing of the pump.
 9. A hydraulic pressure generating device as claimed in claim 7 in which an adjusting means is provided for adjusting a setting pressure of the pump from the outside of the tank. 